1. Field of the Invention
This invention relates to a fuel supply system for a direct fuel injected engine and more particularly to an improved fuel supply arrangement that is the most suitable for a direct fuel injected engine used in outboard motors.
2. Description of Related Art
As is well known, in all fields of engine design there is an increasing emphasis on obtaining more effective emission control, better fuel economy and, at the same time, continued high or higher power output. This trend has resulted in the substitution of fuel injection systems for carburetors as the engine charge former. In the common systems used, fuel is injected into an intake air manifold. In order to obtain still further improvement, direct injection systems are being considered. These systems inject fuel directly into the combustion chamber and thus have significant potential advantages.
This direct injection, however, means that the pressure for injecting fuel into the combustion chamber is higher than with manifold injection systems wherein the pressure is at substantially atmospheric or even below. Electric pumps are not totally capable of supplying such high pressures.
In order to supply the necessary pressure for a direct cylinder injection, it has been proposed to employ a fuel supply system of the type used with manifold injection systems with the addition of a high pressure mechanical pump to supply the pressures required for direct cylinder injection. This is comprised of an engine driven pump which supplies fuel to a vapor separator in which the electrically operated fuel pump that is driven off of the engine and which can generate higher pressures as required by the direct injection system. This type of system can be quite effective.
However, in connection with outboard motors, the direct injection system causes problems in other aspects.
Heretofore, engines which employs this kind of direct high pressure fuel injection system are provided with components such as a high pressure fuel pump, a pump drive unit, a high pressure regulator, fuel injectors and fuel supply rails. In automobile engines, generally all of these components are mounted on a cylinder head member. Some of or all of the components are unified together to form a high pressure fuel injection assembly and then mounted on the cylinder head member. However, since each component has own tolerance, the high pressure fuel injection assembly holds accumulated tolerances. Also, the engine, on which the high pressure fuel injection assembly is mounted, per se contains accumulated tolerances. In addition, these components generate vibrations during the engine operation. In order to absorb the accumulated tolerances and the vibrations, usually, the automobile engines employ metal pipes that allow small deformations, as a part of high pressure fuel delivery pipes.
However, if the components are mounted on different portions of the engine relative to each other, for example, the cylinder block and the cylinder head member, the accumulated tolerances and the vibrations are not absorbed very well even though such metal pipes are used. One reason for the inferior absorption of the vibration is that each portion of the engine has own characteristic frequency.
Generally, outboard engines have this arrangement. That is, in the outboard engine, since cylinders are vertically spaced, the fuel supply rails supporting the fuel injectors are mounted on the lateral part of the engine, i.e., the cylinder head member. In the meantime, the high pressure fuel pump and the pump drive unit are mounted on the upper part of the engine, i.e., the cylinder block.
A jig is useful for assembling the fuel injection unit and the differences between respective components are considerably adjusted. However, mounting eyes or bosses on the engine still slightly vary from each other due to respective tolerances of the engine parts. Thus, if knock pins would be provided on the engine parts, the high pressure fuel injection assembly might not be mounted onto the engine.
Also, usually, the abovenoted metal pipes are merely made of an iron-base material with surface treatment such as plating. This can give rise a problem of corrosion particularly with the outboard motors that are used at sea. In addition, such metal pipes may cause metal fatigue. This is a serious problem with the outboard motors. Because, generally the engines for outboard motors have much vibration even under normal running conditions. In addition, due to the allowed deformations, the metal pipes are somewhat inferior in rigidity or stiffness and tend to invite deterioration in endurance when much stress is exerted. Incidentally, rubber-base materials are not suitable for engines because they are incompatible with the fuel such as a gasoline.
It is, therefore, a principal object of this invention is to provide a fuel supply arrangement for a direct fuel injection system whereby problems with accumulated tolerances, vibrations and corrosions can be resolved, which occur when mounting a high pressure fuel injection assembly onto an engine.
It is another object to provide a method of assembling the fuel supply arrangement, particularly that may provide an easy positioning of the components that form a high pressure fuel injection assembly.
This invention is adapted to be embodied in a direct fuel injected system for an internal combustion engine.
In accordance with one aspect of this invention, the fuel injected system has a high pressure fuel pump for developing high pressure in fuel. A fuel injector is provided for directly injecting the fuel into combustion chamber of the engine. A flexible conduit is provided for connecting the high pressure fuel pump and the fuel injector.
This invention is also adapted to be embodied in a direct fuel injected system for a multi-cylinder internal combustion engine.
In accordance with another aspect of this invention, the fuel injected system has a high pressure fuel pump for developing high pressure in fuel. A plurality of fuel injectors are provided for directly injecting the fuel into respective combustion chambers of the engine. A fuel supply rail is provided for supplying the fuel from the high pressure fuel pump to the fuel injectors. A flexible conduit is provided for connecting the high pressure fuel pump and the fuel supply rail.
In accordance with a method of practicing one feature of this invention, the direct fuel injected system is for a multi-cylinder internal combustion engine that includes the abovenoted components therein. The method includes the step of temporarily connecting both of the high pressure fuel pump and the fuel supply rail relative to each other by means of a temporary member. The step of temporarily affixing the temporary member to the engine is also included. The step of fixing the high pressure fuel pump and the fuel supply rail to the engine is further included. The step of removing the temporary member from the engine is also included.